RE: IML: 68 No-start when hot

["Bob Oyen" <boboyen@xxxxxxxxxxx>]

Black Smoke when it starts is fuel (unburned). 


Bob Oyen
Oyen Consulting
Mitchell 1 Independent Sales Rep
925-586-4105

-----Original Message-----
From: mailing-list-owner@xxxxxxxxxxxxxxxx
[mailto:mailing-list-owner@xxxxxxxxxxxxxxxx] On Behalf Of
mopar413@xxxxxxxxxxx
Sent: Tuesday, September 11, 2007 5:59 PM
To: mailing-list@xxxxxxxxxxxxxxxx
Cc: Greg Krueger
Subject: RE: IML: 68 No-start when hot

Is the starter turning the engine over like it does when cold.  If it turns
slow then  you have heat soak in the starter.
---- Greg Krueger <box_89krueger@xxxxxxxxxxx> wrote: 
> 
>        Yes the car is in running condition i have driven it 100 miles at a
time. I am fairly certain it is in the fuel system not the electrical.
Black smoke will blow out of the tail pipe momentarily after I get the car
finally started.  We have replaced the coil, ballast resistor, spark plugs,
and wires.  We have checked for spark and it is there even when the car will
not start.  Also emedietly after I have realized the car wont start i check
the carb's choke it is working as it should.  I am fairly certain this is a
boil over problem on a rebuilt holly carburetor. any advice.  
> 
> 
> From: sosmi@xxxxxxxxxxxxx: mailing-list@xxxxxxxxxxxxxxxxxxxxxxx: Re: 
> IML: 68 No-start when hotDate: Tue, 11 Sep 2007 19:52:14 +0000 Since there
has been a lot of very good input, I would only add, spark, and fuel. The
two easy tests. It is possible the accelerator pump is in-active. The 68
should have a Holley carb, it's possible the cold start is good because the
choke is closed, and vacuum during cranking will draw enough fuel to start,
once the engine is hot it may be too lean to start. Then when the engine
cools enough the choke may close enough to start. A simple check to see if
the accelerator pump is working would be in order. And as others have
stated, check for spark, however I have the impression the engine will
start, only with delay. If that's the case,it's most probably a carb/fuel
issue. A very low fuel pressure, or blocked fuel filter may also be a
problem. You also didn't say if the car was driveable .Ya'll have a nice
day, Dave.
>  
> -------------- Original message -------------- From: "Geoff Fors" 
> <wb6nvh@xxxxxxxx> > It sounds like the fuel is boiling and/or 
> vapor-locking in the carburetor > bowls. I presume that once the 
> engine is running, it doesn't stall when > hot, it just won't re-start 
> when hot? That points to a fuel system problem. > I also presume this 
> is running a Carter AFB series carburetor. > > Sounds like the heat 
> riser valve is frozen in position, and its thermal > clock spring may 
> be rusted away or missing as well. The spring keeps it > closed until 
> the engine heats up, then it holds it open after that. The > exhaust 
> force will also push it open when the engine is brought above idle. > 
> It's possible to wire the heat riser open, especially if you live in a 
> warm > climate. However, the heat riser assists in rapid warm-up and 
> reduces the > time that excess gasoline enters the combustion chambers 
> during warm-up. > You may have a valve which is rusted closed, even 
> though it appears to be > open from an exterior view. That would 
> certainly account for this problem. > Sometimes the paddle moves on 
> its shaft. The only way to tell is to drop > the exhaust pipe from the 
> manifold and look, rather a pain. > > It's not unheard of for the heat 
> riser paddle to come off the shaft and fall > down the pipe, jamming 
> at some point, plugging that side. I haven't seen > this on Imperials 
> but on 1960's Buicks it will totally plug the exhaust > system! > > 
> The gasoline sold today tends to vaporize far more quickly than 1968 > 
> gasoline and thus older cars without fuel injection can vapor-lock 
> easily. > This is a perennial subject in other make car clubs at the 
> moment. > > The paint always cooks off on the heat r iser path section 
> of the intake > manifold after awhile. That's normal. It shouldn't 
> come off the rest of > the manifold, however! > > If we were to take a 
> survey, I think you will find that there are quite a > few of us 
> running stock '67-'68 setups with working heat riser valves and > 
> original carbs and gaskets, and we don't have this hot-start issue. 
> Thus I > think something is wrong. It wouldn't hurt to make sure the 
> choke is fully > pulled-off when the engine is warmed up. The setup 
> worked fine originally, > so if it isn't doing so now, something is 
> not right. > > I don't see any point in changing the intake manifold. 
> The heat comes from > the riser tube, not the manifold design. If you 
> really want to eliminate > the heat, use a gasket that blocks the 
> riser tube holes, and you can retain > the stock manifold. And, it 
> wouldn't hurt to use a thicker gasket under the > carb. Bu t, it 
> should run fine as a stock setup, and not get too hot. > > Geoff > 
> Monterey CA > > > ----------------- http://www.imperialclub.com 
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